ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Melting temperatures, heats of fusion and the derived enthalpies and entropies of fusion were obtained by differential scanning calorimetry for poly(ethylene oxide) (PEO)-acrylate and -methacrylate macromonomers and the corresponding polymers. The side-chain lengths varied from three to ninety-three ethylene oxide units. The thermodynamic data for macromonomers and polymers were calculated according to the theory of Flory and Vrij, which has been shown to describe well the melting behavior of linear PEO. It is shown that the melting parameters for macromonomers are identical to those of pure PEO in spite of the presence of the chain ends of different nature. With the PEO comb-like polyacrylates and polymethacrylates, the melting points are only a few degrees higher than those of the corresponding monomers. Their crystalline content calculated from the molar enthalpies are 83% and 78%, respectively. In contrast to linear PEO, the interfacial free energy is negative for both types of polymers due to a high value of the interfacial entropy. It is suggested that the tighter packing of the chain ends, including the backbone, is responsible for this high value, together with the possible presence between the lamellae of constructed amorphous side chains. The combined results lead to the conclusion that the crystalline organization is quite comparable to that of pure PEO of equal length with, however, one or two fewer crystallized EO units.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1990.021910521
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